BMS218 > Compatibility Testing > Flashcards

Compatibility Testing Flashcards

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1
Q

Why might a blood transfusion be required?

A

Trauma
Surgery
Leukaemia support

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2
Q

What is transfused to treat anaemia?

A

Packed Red Blood Cells

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3
Q

What is transfused to treat thrombocytopaenia?

A

platelets

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4
Q

What is transfused to replenish clotting factors?

A

Plasma

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5
Q

Do all patients require whole blood transfusions?

A

No, many patients only require specific blood components or sub-fractions (e.g., PRBCs, platelets, or plasma).

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6
Q

What are the alternatives to blood transfusion for anaemia during pregnancy?

A

Administration of folate, iron, and B12
Bypass risk from transfusion altogether

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7
Q

What are the key factors to consider before performing a blood transfusion?

A

Recipient’s blood group, immune status, current clinical condition, and donor’s blood group

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8
Q

How does the recipient’s immune status affect transfusion decisions?

A

Need to know if they have clinically significant/reactive antibodies

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9
Q

What does a patient’s current status affect?

A

If they have critical blood loss they require product now.
Less critical means they have more time to find the most compatible match.

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10
Q

Why do you need to know the donor’s blood group?

A

Donor cells are washed to remove residual plasma and antibodies that could cause allergic or immune reactions in the recipient, but you can’t wash off the antigens on the RBCs, so they have to match the recipient

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11
Q

What causes immune-mediated transfusion reactions?

A

They occur when incompatible blood products are transfused, triggering a patient immune response against donor cells.

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12
Q

What type of reaction occurs when incompatible RBCs are transfused?

A

A haemolytic transfusion reaction (HTR)
It can be acute (immediate) or delayed.

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13
Q

What reaction can result from incompatible donor WBCs?

A

Febrile non-haemolytic transfusion reaction (FNHTR)

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14
Q

What reaction can occur from incompatible donor platelets?

A

Post-transfusion purpura (PTP)

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15
Q

What are common symptoms of transfusion reactions?

A

Chills, fever, shaking, and aching

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16
Q

Which transfusion reaction is mild and often resolves on its own?

A

Febrile non-haemolytic transfusion reaction (FNHTR)

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17
Q

Which transfusion reaction can be life-threatening?

A

Acute haemolytic transfusion reaction (HTR)

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18
Q

How can transfusion reaction risks be minimised?

A

Only use blood products when necessary

Use specific components rather than whole blood

Leukodepletion to remove white cells from donations.

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19
Q

What does leukodepletion do?

A

Reduces the risk of certain infections as well as the risk of fever due to white blood cell incompatibility.

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20
Q

How are leukocytes separated?

A

On the basis of size, dielectric properties, by affinity separation, freeze-thawing, centrifugation and filtration

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21
Q

What is the purpose of compatibility testing?

A

Provision of the appropriate, compatible blood and/or blood
product to the right patient in an appropriate time frame

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22
Q

What are the requirements of compatibility testing?

A

Patient identification and sample collection.
Compatibility testing
Correct documentation

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23
Q

What are the steps of compatibility testing?

A
  • ABO and Rh grouping (for the patient & donor)
  • Antibody screening (patient only)
  • Selection of donor units
  • Cross-matching (between patient plasma and donor cells)
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24
Q

What is the purpose of pre-transfusion testing?

A
  • Identify ABO and Rh(D) status of patient & potential donor (Group matched blood)
  • Detect (screen for) antibodies in patient plasma against donor RBC antigens
  • Document findings to ensure accuracy
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25
What do the results from pre-transfusion testing define?
The results define what donor units to ask the blood bank for
26
What are the requirements for donor blood materials used in compatibility testing?
Donated materials need to be within the expiry date
27
What are the requirements of patient samples?
* Non-haemolysed sample * Collected within 72 hours of transfusion
28
What causes restrictions on what RBC donations a patient can receive?
Recipient antibodies restrict what RBC donations a patient can receive Recipients will (may) have antibodies against antigens they do not have on their own cells
29
What antibodies does an O negative person have?
Anti-A, B, AB and RhD.
30
Why is O neg the universal donor?
O-negative RBCs have no A, B, AB or RHD antigens on cells, so they can be given to all blood types.
31
What antibodies does an AB-positive patient have?
They have no ABO or Rhesus antibodies. No Anti-A, B, AB, or RhD, because these are the antiens expressed on their cells.
32
Why is AB-positive the universal recipient?
Because they have all the antigens, they can only donate to other AB-positive people. Because they have no antibodies, they can receive RBCs from any of the ABO blood types and not get a reaction
33
What are the ABO and Rh(D) grouping requirements for the donor?
“Group check” – recheck donor unit(s) to make sure they match what the bag says. ABO forward group only because there is no plasma Rh(D) group
34
What are the ABO and Rh(D) grouping requirements for the patient?
ABO forward and reverse groups Rh(D) group
35
During antibody screening, what does a reaction indicate?
Any reaction indicates that an antibody is present
36
What type of antibodies should be detected in antibody screening?
clinically significant antibodies
37
What testing method is used for detecting clinically significant antibodies?
The Indirect Antiglobulin Test (IAT) using red cells suspended in LISS (a defined salt solution)
38
At what temperature is antibody screening performed?
Initially at room temperature, then 37°C, which is optimal for detecting IgG antibodies that react at body temperature.
39
What are acceptable techniques for IAT testing?
Column Agglutination Technology (CAT) Liquid-phase testing Solid-phase testing Other methods may be considered, e.g. enzymes
40
How is a detected antibody fully identified?
Full identification using a fully typed long cell panel (usually 11 cell)
41
What does the 3 cell panel tell us?
Is there a clinically significant antibody, which isotype is it, and at what temperature is it reactive?
42
What blood group should be used for antibody screening cells?
Group O red cells
43
Why are Group O red cells used for antibody screening?
So patient anti A & B don’t react with test cells, and we can see if there are other significant antibodies other than those from the ABO system.
44
What Rh phenotypes must be represented in an antibody screening panel?
One R1R1 (DCe/DCe) cell One R2R2 (DcE/DcE) cell
45
Which red cell antigens should be expressed on screening cells?
C, c, D, E, e, M, N, S, s, K, k, Fya, Fyb, Jka, and Jkb.
46
Which antigens must be represented in homozygous form to detect dosage?
Jk(a+b–) Jk(a–b+) Fy(a+b–) Fy(a–b+) S+s–S–s+ C or c E or e K or k M or N Lea or Leb
47
What is the first priority when selecting donor units for transfusion?
To match the patient’s ABO and Rh(D) blood group as closely as possible.
48
What blood type is used if ABO-compatible blood is not available?
Group O negative red cells, as they lack A, B, and Rh(D) antigens.
49
What do you do if a patient has 37°C reactive antibody?
Match them with a donor with cell negative for the antigen.
50
What does it mean if an antibody is not reactive at 37°C?
It means that it may not be clinically significant because it won't react at body temperature.
51
How do we know donor cells are compatible?
If they do not react at the IAT stage, this means there are no antibodies in the patient plasma reacting with the donor cells, even after incubation and IAT.
52
What risk exists if a patient is transfused with antigen-positive cells they don’t yet have antibodies against?
The patient may become alloimmunised and develop new antibodies against that antigen. This can lead to future haemolytic transfusion reactions (HTR)
53
What is detected at the immediate spin?
clinically sigificant IgMs
54
What is detected after 37 degree incubation but before IAT?
Body temperature reactive IgMs
55
What is detected at the IAT phase?
37 degree reactive IgGs, they don't get shown until after the green goo (AHG reagent) is added.
56
What is involved in serologic cross-matching?
Mix donor cells with patient plasma. Immediate spin cross-match IAT cross-match.
57
What is an Immediate Spin (IS) crossmatch used for?
When the patient has no history of atypical or unexpected antibodies, it checks ABO compatibility only
58
What is an IAT (Indirect Antiglobulin Test) crossmatch used for?
History of atypical/unexpected blood group antibodies History of previous blood group antibody detection
59
What are the causes of a positive cross-match (agglutination)?
Incorrect ABO grouping of patient or donor Alloantibody in patient serum reacting with donor red cell antigens Autoantibody reacting with donor red cell antigens DAT positive donor red cells Abnormalities in patient serum Contaminated test system
60
What does a positive cross-match mean?
Patient and donor NOT compatible
61
What is an electronic crossmatch?
Compares recent serological results for both patient and donor Determines compatibility based on comparison
62
How safe is the electronic crossmatch compared to immediate spin?
Demonstrated to be as safe as immediate spin
63
What are the advantages of electronic cross-matching?
Safer Cheaper Quicker
64
When is an electronic cross-match permitted?
When: - The laboratory has a comprehensive, validated, electronic data management system - a valid pretransfusion specimen has been tested in accordance with the requirements given in 2.5 and 2.6 - The patient has no clinically significant antibodies or no history of such antibodies
65
Is compatibility testing a guarantee that donor red cells will survive in vivo?
Compatibility testing is not an absolute guarantee of in vivo survival.
66
67
What are the limitations of compatibility testing?
It will not prevent immunisation; there could still be a reaction as antibodies are developed against antigens not already present in the patient. It will not detect all errors of Rhesus typing; there could be anomalies. Will not detect all antibodies present; there are a lot more antibodies than just the ones on the 3 and 11 cell panels Must be correctly performed
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